In general, a tool comprising a coating film of a nitride or a carbonitride of AlTiSi on a base surface of WC-based cemented carbide, cermet or high-speed steel in order to improve wear resistance and provide a surface protecting function is known as a cutting tool or a wear-resistant tool (refer to patent document 1 identified below, for example).
In response to the recent trends described below, however, the cutting edge temperature of a tool tends to increasingly rise in cutting, and characteristics required of tool materials are becoming more severe. For example,
1. dry working with no lubricant (coolant) is required in consideration of terrestrial environmental protection,
2. worked materials (workpieces) are diversified, and
3. the cutting speed is increased in order to further improve working efficiency, can be listed.
In this regard, patent document 2 identified below, for example, discloses that the performance of a cutting tool is improved also in dry high-speed cutting by providing a TiN film immediately on a base while providing a TiAlN film thereon and further providing a TiSiN film thereon. According to this patent, it is possible to solve such a problem that intra-film diffusion of oxygen can be suppressed due to an alumina layer formed by oxidation of a film surface during cutting when a TiAl compound film is provided as a coating film, while the alumina layer is so easily separated by a porous Ti oxide layer formed immediately under the alumina layer upon dynamic cutting that the progress of oxidation cannot be sufficiently prevented in general, the aforementioned porous Ti oxide layer is not formed but improvement of performance is attained by providing a dense TiSi compound film having extremely high oxidation resistance on the film surface.
Patent Document 2: Japanese Patent Laying-Open No. 2000-326108